1. Field of Invention
The present invention relates to an antenna and a communication device that includes the antenna. More particularly, the present invention pertains to a Global Positioning System (GPS) antenna in a communication device.
2. Description Related Art
In recent years, portable communication devices have become very popular. In view of their ubiquity, such devices may be very useful in contacting emergency personnel, as it is likely that a person owning such a unit will be present at the scene of an accident or crime. As such, the Federal Communications Commission (FCC) has mandated certain standards for reliable operation of GPS applications in portable communications devices.
Although almost all portable communications devices meet or will meet the FCC standards, the reception associated with most GPS antenna is sometimes poor. In many cases, the problem is caused by difficulties associated with synthesizing an antenna pattern optimized for GPS satellite reception. In particular, many portable communications devices rely on the main subscriber antenna to capture GPS signals. Unfortunately, if the communication device is in a typical vertical position, such as clam-shell cellular phone, the main lobe of the GPS radiation pattern is generally pointed downward, which reduces the link margin with GPS satellites transmitting from the upper hemisphere. In fact, in many cases, the GPS radiation pattern features a null pointing upward towards the GPS satellites. Radio frequency (RF) currents flowing on the phone chassis, particularly the lower portion of a clam-shell handset, are generally seen as the root of this problem.